assuming we are talking about ww2. The main difference is that the majority of battles in the pacific, we're amphibious assaults fought on islands. sometimes tiny islands thousands of miles from major land masses. The Pacific had several naval battles that were instrumental in the outcome of the war. Most battles were in hot humid climate where malaria and other tropical diseases were contracted by the majority of men fighting. European theatre was at times cold with snow, fight on continent and countries. the majority of men in Europe were army and the majority of the Pacific were Marines.